In a large number of industrial processes, control of the flow rates of a variety of processing fluids is necessary, and for this purpose a flow rate control device is provided on the flow path of these processing fluids.
Flow rate control devices such as this are required to be able to rapidly and stably control the flow rate of processing fluids at desired values (i.e., at target flow rates). Because of this, as is shown in Patent document 1, the valves and flow rate sensors and the like that are used, for example, to adjust the flow rate in a conventional flow rate control device are those having the best possible responsiveness, and these are then tuned so that they perform to their maximum capabilities regarding responsiveness and stability.
However, in a semiconductor manufacturing process in which a plurality of processing gases are used while the respective flow rates of each gas are controlled, if a high-performance flow rate control device having superior responsiveness is introduced in place of the flow rate control device already being used, then defects such as the final product (i.e., the semiconductor) not conforming to the desired specifications sometimes arise.
As a result of strenuous investigations, the applicants of the present invention discovered the cause of these defects.
Namely, conventionally, using the current flow rate control device, a processing recipe is determined via trial and error such that the final product (i.e., the semiconductor) has the desired specifications and performance. ‘Processing recipe’ refers, in the case of processing fluids, to the quantities of processing fluids and the timings when they are used. In other words, the processing recipe dictates how target flow rates for each processing fluid should be set.
However, the flow rates of the processing fluids that are actually used do not always accurately follow the target flow rates dictated on paper in the recipe, and sometimes delays (lags) are generated in the flow rate depending on the responsiveness of the flow rate control device.
Accordingly, if the current flow rate control device is replaced with a high-performance flow rate control device, because this new high-performance flow rate control device more precisely follows the target flow rate, the actual flow rate ends up being different from the conventional flow rate (i.e., from the recipe actually being implemented) which has not adequately followed the target flow rate, and the possibility arises that the final product will not conform to the specifications.
Because of this, conventionally, when a flow rate control device is replaced with a new type of apparatus or the like, an on-site operator who actually sets the flow rates of the processing gases has to correct the recipe, in other words, correct the target flow rates, once again via trial and error, and, particularly when a large number of processing fluids are used, this requires massive amounts of time and effort.